This invention relates in general to wireless communication and wireless communication systems, and more particularly to dispatch communications involving dispatch calling parties administered by different dispatch communication controllers.
There are numerous mobile or wireless communication systems in use today, and these provide a wide variety of modes of communicating. Perhaps the best know today is the cellular radiotelephone communication system. Other systems are also in widespread use, such as trunked radio systems used by public safety and law enforcement agencies. These latter communication systems provide what has been referred to as dispatch communication. Dispatch communication is half-duplex communication, where, when one person is speaking, the other(s) can only listen. This is different than, for example, telephone communication, which is duplex, and both parties in a call can speak and listen simultaneously. Dispatch communication has an advantage in that call set up time is very low, and typically users need to simply press a button to begin talking to the other party or parties. In many typical dispatch communication systems there is a dispatcher that monitors the communication activity, and can facilitate communication among parties. The dispatcher, unlike other parties communicating through the system, typically is in a fixed location. In many of these communication systems users may be grouped together to form talk groups. When any member of the talk group speaks, all the members of the talk group that are available hear the speaker""s voice. While the speaker is speaking, no other member can speak to the talk group members, although typically the dispatcher can over-ride the speaker. Conventional trunked radio systems are usually closed systems. That is, they are not open to the public, and are used exclusively by some organization, or perhaps shared by several governmental agencies. As such, the operators of the system have direct access to the communication system equipment. One advantage of having direct access is the ability to patch talk groups together, which is useful under certain conditions, such as emergency management. The drawback of these systems is that they can be extremely expensive to purchase and to operate, and therefore are not cost effective for small businesses and agencies.
The cost of purchasing and operating a dispatch communication system is more than most small organizations are willing or able to spend. This created a need in the marketplace for inexpensive dispatch communication service, and this need has been addressed by communication system operators that provide such service. Specifically, the operators provide both private call dispatch calling, which is half-duplex communication between two individuals, and talk group calling. Typically these services are offered along with mobile telephone service so that with the same mobile communication device a user can engage in any of the three modes of communicating. For talk groups, the user must belong to predefined talk group. To set up a talk group an organization provides a list of users to the communication system operator for each talk group the organization wishes to have. The communication system operator then defines a talk group comprised of these users by creating a talk group record in the communication system. Each mobile communication device is assigned or affiliated with an identifier. These identifiers are used by the communication system to interact with the mobile communication device and provide communication service. Furthermore, the mobile communication devices are designed to be operated much like a two-way radio for private and group dispatch calls. That is, the mobile communication devices are provided with a xe2x80x9cpush to talkxe2x80x9d (PTT) button, and a user interface including a keypad and a display. The user selects the mode of communication, and an identifier or alias associated with the individual or group with whom the user wishes to communicate with, and presses the PTT button. The mobile communication device then sends the information, over the air interface, to the communication system, which sets up the call, locates the call participants, and sends a xe2x80x9creadyxe2x80x9d message back to the initiating mobile communication device, which then alerts the user that the channel is open and the user may commence speaking. Typically the time from pressing the PTT button to getting the channel open alert takes less than one second. While these communication services have provided a cost-effective alternative to purchasing and operating a dispatch communication system, it doesn""t provide the flexibility in configuring communication services that would be needed for small to mid-sized organizations, such as small public safety and emergency organizations. In particular, there is no way for the subscribers to join or patch talk groups together as there is when the organization operates and controls the communication equipment. This is because in the conventional subscriber dispatch communication systems there can be as many as 15 or more dispatch communication controllers servicing an urban area to handle the high number of subscribers. Conversely, in a proprietary system, there is typically only a need for a single dispatch communication controller. Therefore there is a need for a means by which subscribing organizations can patch together talk groups, even though they are only subscribers, and not the operators of the communication system.